Functional Sufficiency of Coastal Blue–Green Adaptation: Hydro-Institutional Evidence from Chennai and Kochi, India

Abstract

Coastal adaptation requires a direct contrast between the level of local climate pressure and the utility provided by the functions associated with the blue-green action. In this case, we focus on Chennai and Kochi, Indian coastal cities facing climate pressure from exposure to sea-level rise, heavy rain, warming, drainage challenges, and land use. These two cities experience all five pressures without generating similar climate adaptation needs. Hydro-Institutional Adaptation Partitioning (HIAP) is used to translate the values of 2080 climate projections and planning actions into four pairs of dimensions that include: thermal pressure, sea-level pressure, rainfall-regime pressure, and extreme-event pressure. The planning cover was operationalized based on national policy and planning program support, climate planning, wetland/biodiversity projects, and participation in canal governance. It is observed that the two cities had a consistent number of action classes of four, yet different adaptation needs. Chennai has the larger sea-level coefficient than that of Kochi and maintains small uncovered pressure in both thermal and sea-level dimensions. On the other hand, Kochi has the highest overall climate pressure due to high levels of warming and decline in mean rainfall. The latter also maintains the larger uncovered pressure related to thermal moderation and rainfall retention capacity. Sensitivity tests revealed that the uncovered climate pressure in Kochi increased with respect to heat-dryness weighting, whereas Chennai stayed responsive to sea-level drainages and heat sensitive open spaces.